Thundersky Cells

[Technologic]

I've read the thread at diy...
and I don't understand, why they constantly talk about charging with 4.2Volt. Isn't it a 90AH LiFePO cell?
3.65-3.85Volt is usually the cutoff for them. 4.1Volt absolute maximum.

And the overcharge situation has no effect in voltage drop. At least the cell wouldn't recover, if it was damaged by overcharge.
Poor connections and thin cables where the reason for the huge voltage drop. (but that was mentioned before)

-Olaf
evisol.com

Sky Energy had on their website 4.25v charge as of 2 days ago, but has now changed it to 3.9v.

I can adjust it fairly simply, but they show a full charge voltage of something like 4.3v on their charts.
http://www.thunder-sky.com/pdf/20092201190.pdf

As you can see Thunder sky's "same cell" specs the same 4.25v charging.

I personally have been using 4-4.1v and simply winding it down to 3.7-3.9 after the cell reaches 3.6v or so on the charging phase.

I'll have to ask them about their BMS and charger to see what the output voltage they're specing for as well... 3.9v (or lower) is probably much better for life cycle.

 

[Doctorbass]

What I wonder is if Thundersky are really LiFePO4 cells chemistry.. cause it seems to be the only one that charge up to 4.2V..

The only high power lithium ion i know that charge to 4.1-4.1V and that have a very similar discharge curve are the Lithium manganese chemistry. but their nominal voltage is 3.7V and not 3.3 like LiFePO4...

for the T-S,
If the recommandation of SOC range of use is 80% that would mean they can work in the 10 to 90% soc.. so the 4.1V is never reached and is almost 3.8-3.9V whne charged

Doc

 

[Technologic]

What I wonder is if Thundersky are really LiFePO4 cells chemistry.. cause it seems to be the only one that charge up to 4.2V..

The only high power lithium ion i know that charge to 4.1-4.1V and that have a very similar discharge curve are the Lithium manganese chemistry. but their nominal voltage is 3.7V and not 3.3 like LiFePO4...

for the T-S,
If the recommandation of SOC range of use is 80% that would mean they can work in the 10 to 90% soc.. so the 4.1V is never reached and is almost 3.8-3.9V whne charged

Doc

Well the nominal voltage is def 3.2v on these... not sure what it could be outside of thundersky just overspecing.

I can chop up the battery after testing if anyone has access to a chemical analyzer.

 

[AndyH]

Guys - take a look at the Thunder Sky manual - it makes it clear that the voltage range for their LiFePO4 cells for a 2000 cycle life is between 2.5V and 4.3V.

http://www.thunder-sky.com/pdf/2007030222.pdf 9.08MB

Andy

 

[monster]

if you search you tube for thundersky there is some guy who bought loads of them for an electric car and had a 20% failure rate. TS welshed on their returns policy too!

 

[olaf-lampe]

...

for the T-S,
If the recommandation of SOC range of use is 80% that would mean they can work in the 10 to 90% soc.. so the 4.1V is never reached and is almost 3.8-3.9V when charged

Doc

That depends on the charge current. With higher currents you'll reach 4.1V probably at 70% SOC. With smaller currents you are more in the area of 90%.
The only solution to find out, is to discharge a cell at 1C to 0% and then charge up to 80% with a capacity meter and write down the voltage (and temperature).

-Olaf

 

[fechter]

It seems fairly intuitive that you want to use the lowest voltage that will still give you a 100% charge. All battery chemistries are adversely affected by excessive charging voltage.

Minimum voltage needed for a full charge is typically affected by temperature with most chemistries, but I don't know how much LiFeP04 is affected.

I suspect the TS specification is the highest voltage the cell can tolerate without failing immediately. Long term may be another story.

 

[Doctorbass]

for the A123, this is what i found

A123 cell spec sheet
Recommended charge and cut-off V at 25°C 3.6V to 2V
Recommended charge and cut-off V below 0°C 4.2V to 0.5V


It seems that due to the higher RI at low temp, that to carry the right current to charge it it need to have a Voltage increase.

Operating temperature range -30°C to +60°C
Storage temperature range -50°C to +60°C


also on another A123 spec sheet:

Maximum recommended charge voltage: 3.8V
Maximum allowable charge voltage: 4.2V MAX


they say... Allowable.... :? .. for me that mean before danger!!.. I know some guys tried to charge it at 5V and up and at 5.2V it exploded.. poped.. but no fire..

Doc

 

[Technologic]

if you search you tube for thundersky there is some guy who bought loads of them for an electric car and had a 20% failure rate. TS welshed on their returns policy too!

I haven't seen many people with thunderskys to receive any sorts of information.

But a 20% failure rate and 1500 cycle life is certainly much more sane than paying Yesa $2/AH

Likewise the sales practices of Sky Energy could be different than Thundersky... there's really no telling.
Until companies like Yesa make their products at reasonable prices... buying two sets of Sky Energy's are still cheaper (20kwh vs 10kwh of Yesas).

It's sad to think in such terms, but it's also a bit silly to expect customers to pay twice as much for quality differences that are questionable and almost unverifiable without sample testing.

 

[AndyH]

if you search you tube for thundersky there is some guy who bought loads of them for an electric car and had a 20% failure rate. TS welshed on their returns policy too!

Yes - that was quite a while ago, and they were white cells, not LiFePO4.

 

[AndyH]

It seems fairly intuitive that you want to use the lowest voltage that will still give you a 100% charge. All battery chemistries are adversely affected by excessive charging voltage.

Minimum voltage needed for a full charge is typically affected by temperature with most chemistries, but I don't know how much LiFeP04 is affected.

I suspect the TS specification is the highest voltage the cell can tolerate without failing immediately. Long term may be another story.

I agree with all you're written here. For the rest, I'm only reporting what TS has advised.

See page 16 in the TS Battery manual. For their LiFePO4 cells, they show 4.5V as 100% capacity, max charge to 4.3V (95%?). On page 17 they say discharge can be between 2.0 and 2.5V without damage. Same page - for more than 2000 cycles, keep voltages between 2.5 and 4.3.

Adjusting for temperature is discussed starting on page 28.
- For 25C, min 2.5V max 4.25V
- for minus 35C, 1.5V to 4.3V (adjust voltages when cell temperature climbs)

Normal charge and discharge is .3C, max is 3C.

The Chinese maxi-scooters being sold in the US that use TS cells have the controller's pack level LVC set at 2.5V per cell. The TS-supplied charger is 15A for the 60AH cells, and 10A for the 40Ah cells - .25C charge.
The charger supplied for 21 of the 60Ah cells is 77V nominal - 3.67V per cell. I've seen 80V on a pack during charging - 3.8V per cell average.

 

[Technologic]

It seems fairly intuitive that you want to use the lowest voltage that will still give you a 100% charge. All battery chemistries are adversely affected by excessive charging voltage.

Minimum voltage needed for a full charge is typically affected by temperature with most chemistries, but I don't know how much LiFeP04 is affected.

I suspect the TS specification is the highest voltage the cell can tolerate without failing immediately. Long term may be another story.

I agree with all you're written here. For the rest, I'm only reporting what TS has advised.

See page 16 in the TS Battery manual. For their LiFePO4 cells, they show 4.5V as 100% capacity, max charge to 4.3V (95%?). On page 17 they say discharge can be between 2.0 and 2.5V without damage. Same page - for more than 2000 cycles, keep voltages between 2.5 and 4.3.

.

4.25v is the LFP's max capacity according to the charts... only testing will prove if this is correct.

You also need to charge it at low amperage for more than 1 hour at 4.25v to go from 80% to 100% charge... something that's somewhat questionable to me.

 

[pgt400]

So far, I'm wondering if Thunder Sky is buying Ping cells and putting them in a heavy box. :wink:

Andy

Why? low C rating? Are you at least getting 60ah out of them?

 

[Technologic]

So far, I'm wondering if Thunder Sky is buying Ping cells and putting them in a heavy box. :wink:

Andy

Why? low C rating? Are you at least getting 60ah out of them?

I've gotten over 90AH out of my TK90AHA ... when I actually complete the charge.

Even 70% charges are over 70AH

 

[rossasaurus]

Sky Energy Comment:

wow, that shipping! via personal courier?

SkyEnergy 60AH:
let's see; $75 per cell + 21.45/cell shipping = $96.45/cell

TS via Elite 60AH:
wow, their prices went way up...
$120/cell + shipping

Jennifer, why did your prices climb from approx. $1.5/AH to $2/AH in such a short time?

Compared to TS, SkyEnergy seems a bargain, but they're both charging too much. A friend told me the other day that the price was raised and was told by supplier, "well, you're doing well so we raise the price". So he went to HiPower. We need actual competition in the lithium market and watch a Million EV's bloom.

We'll have to be smart consumers and find the suppliers who will offer the best prices with equal product.
Maybe not possible with companies tied to the state. Many large companies in China run by children of the national leaders, past and present.


And the other day on BBC the head of BYD Automotive said "...lithium batteries are extremely inexpensive to produce..."
So they're all milking the market like clever capitalists everywhere.

maybe Evo Morales and/or Ms Bachelet will start building lithium batteries from their lithium supplies...we'll call them the Che40AH, Che60AH etc

R

 

[Technologic]

Sky Energy Comment:

wow, that shipping! via personal courier?

SkyEnergy 60AH:
let's see; $75 per cell + 21.45/cell shipping = $96.45/cell

Your quoted price is about $25/each over the one I was quoted for 60AH with shipping included (since i'd be buying about 70 cells).

I was quoted $66 + $4-6/shipping each (depending on how many I buy and ship at once)

Might want to check into that again, or check into a group buy tacking your order on with mine soon.

a 40ft container from Shenzhen port to US port costs about $2200 to ship... up to 40,000lbs... take that into consideration (that 100 cells weighing only 200kg would cost the same according to your quotation).